Pneumatic drive for punching, cutting and stamping devices

Abstract

A pneumatic drive for punching, cutting and stamping devices, which have two tool parts which can be moved toward one another, and of which preferably one, at least in the operating position, is fixedly connected to the machine frame, is constructed such that an opening gap, which is as large as possible, is created. Furthermore, when the tool parts are moved together, the pneumatic drive is operated at a low pressure, so that additional safety devices are not needed. A pneumatic cylinder is secured on the movable tool part for this purpose, the piston rod of the pneumatic cylinder being constructed lockably in at least one end position. The piston rod of a pressure clamping element is secured on the piston rod exiting from the pneumatic cylinder. The cylinder of the pressure clamping element is arranged or fixably stationarily and consists of at least two piston cylinder units with one common piston rod, which piston cylinder units are connected one behind the other.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. In a pneumatic drive for punching, cutting and stamping devices comprising two tool parts which can be relatively moved toward and away from one another and of which at least one of said tool parts is fixedly connected to a machine frame, the improvement wherein at least one pneumatic cylinder is secured on a movable tool part, wherein a first piston rod is provided in said pneumatic cylinder, wherein a locking means is provided for locking said first piston rod in at least one end position thereof to said pneumatic cylinder, wherein at least one pressure clamping element is provided which has a second piston rod secured to said first piston rod exiting from said pneumatic cylinder, said pressure clamping element consisting of at least two piston cylinder units operatively connected with said second piston rod, said piston cylinder units including a fluid circuit means connecting said piston cylinder units in series so that an additive force is outputted on said second piston rod, whereby when said first piston rod is locked in said one end position, said piston cylinder units can be activated by supplying fluid to said fluid circuit means to cause said additive force to be outputted to said second piston rod, thereby causing said first piston rod, which is locked to said pneumatic cylinder, and said movable tool part, which is connected to said pneumatic cylinder, to be moved together toward said fixed tool part. 
     
     
       2. The pneumatic drive according to claim 1, wherein said pressure clamping element includes a cylinder which is comprised of annular individual parts connected together, each annular individual part having a center bore for receiving said second piston rod therein, a piston freely movable on said second piston rod and supported on an adjacent piston, each annular individual part further having a recess therein for receiving said piston therein. 
     
     
       3. The pneumatic drive according to claim 2, wherein each piston consists of a flat annular part and a cylindrical sleeve extending axially from both sides of said flat annular part, and wherein a bore extends axially through said flat annular part and said cylindrical sleeve. 
     
     
       4. A pneumatic drive according to claim 3, wherein said flat annular part and said cylindrical sleeve are of unitary construction. 
     
     
       5. A pneumatic drive according to claim 2, wherein each piston is sealed with respect to said second piston rod by an O-ring seal inserted into a bore in said piston. 
     
     
       6. A pneumatic drive according to claim 5, wherein further O-ring seals are inserted into offset inner surfaces of said recesses in each of said annular individual parts, said further O-ring seals providing an operative seal between said piston and its respective annular or individual part. 
     
     
       7. A pneumatic drive according to claim 2, wherein each cylindrical sleeve has a through-going bore adjacent a perimeter thereof for facilitating a loading of both sides of said piston with pressurized air. 
     
     
       8. A pneumatic drive according to claim 1, wherein at least two pneumatic cylinders are provided and are secured to said movable tool part, and wherein at least two pressure clamping elements are provided and are rigidly connected with one another. 
     
     
       9. A pneumatic drive according to claim 8, wherein said pneumatic cylinders connected to said movable tool part have a substantially larger stroke than said pressure clamping elements and are loaded with a relatively low pressure, so that a closing force of less than 15 kg. results. 
     
     
       10. A pneumatic drive according to claim 8, wherein said pressure clamping elements each have a relativley small cylinder volume and a stroke of approximately 3 mm., and wherein said piston cylinder units, which are connected in series, are each dimensioned such that, at a pressure of approximately 6 bar, a pressure force of approximately 600 kp. per piston unit is obtained. 
     
     
       11. A pneumatic drive according to claim 1, wherein said locking means for locking said first piston rod of said pneumatic cylinder includes an expandable and contractible ring movable into and out of an annular groove on said first piston rod, and means for effecting said movement of said ring. 
     
     
       12. A pneumatic drive according to claim 1, wherein said locking means includes a bolt receiving bore in said first piston rod, and a bolt movably guided in said pneumatic cylinder for movement into and out of said bolt receiving bore. 
     
     
       13. A pneumatic drive according to claim 12, wherein locking means further includes a drive means for said bolt, said drive means comprising a further pneumatic cylinder.